The use of automated control systems for controlling the stopping and starting of conveyers, such as those utilized in retail stores, is well known. Typically, such systems are provided at the delivery end of a conveyor belt built into the checkout stand (also referred to herein as a checkstand). When items/products are placed on the conveyer belt by the customer, the conveyer belt is activated (i.e., started) so as to move the items toward the cashier or checkout clerk. The conveyer belt is then automatically stopped when a sensing device detects a break in a light beam from a light source, which occurs when a product on the conveyer belt enters (i.e., breaks) the light beam. It is noted that the light source and the sensing device are positioned within the checkstand such that the light beam is broken by products as the products reach the end of the conveyer belt. As the checkout clerk removes the product from the conveyer belt to check it out, the light beam generated by the light source again strikes the sensing device and, as a result, the conveyor belt is restarted, until the next product on the conveyer belt breaks the light beam. This process continues to repeat itself until all of the products have been removed from the conveyer belt.
U.S. Pat. No. 4,236,604, which is incorporated herein by reference in its entirety, discloses a known control system for use with conveyer belts and checkstands. In addition to the start/stop control mechanism discussed above, the system disclosed in the '604 patent also provided a time control mechanism for automatically stopping the conveyer belt if no product was detected by the sensing means for a predetermined time interval. The system of the '604 patent prevented the conveyer belt from continually running during periods of non-use, such as when there is no customer at the checkstand, thereby minimizing the wear and tear on the belt, and the costs associated with operating the belt.
Notwithstanding the foregoing advances in conveyer belt control systems, problems still remain. For example, in many instances, especially in retail stores, the objects or products being purchased, and therefore placed on the conveyer belt by the customer, are not opaque. Indeed, many of the products are translucent (i.e., allow for partial amounts of light to pass therethrough). When translucent products arrive at the end of the conveyer belt and enter into the light beam path of the photoelectric control system, the light beam is not totally blocked. In this situation, while the translucent object will diminish the intensity of the light reaching the photoelectric receiving device, the reduction in light received by the photosensor is not sufficient to reach a dark-state level or mode (i.e., the photosensor trip point) required to stop the belt from running. When this occurs, the belt continues to run and the translucent products are pushed or forced off the end of the belt. Many of these products are glass or plastic containers that frequently topple over on to the scanner, creating havoc for the checkout clerk. Some of the tall, round containers at times will roll off the checkstand and fall to the floor.
As one can easily conclude, such operation results in significant disadvantages. For example, there can be significant monetary loss due to product breakage. In addition, customer through-put at the checkstand can be significantly decreased due to the cashier spending time retrieving fallen items or performing clean-up for broken items, such as bottles. It is noted that the foregoing problem also occurs when low profile products are placed on the belt, as such low profile products may not prevent enough light from reaching the photosensor so that the photosensor detects a dark-state mode.
Currently, in order to avoid the foregoing problems, many checkout clerks resort to manually operating the power on/off switch of the conveyer belt in order to control the movement of the belt. However, this defeats the purpose of today's sophisticated checkstands which are equipped with photoelectric control systems in order to facilitate employee productivity by means of hands-off operation with regard to controlling the conveyer belt. In addition, the ergonomic advantage offered by positioning the invisible light beam path in a location that automatically stops the products within the proper reach of the checkout clerk is diminished. More specifically, when the checkout clerk controls the movement of the conveyer belt, once the belt is stopped the checkout clerk will begin reaching further up the belt to retrieve products rather than restarting the belt. Thus, when a checkout clerk avoids using the photoelectric control system to control movement of the belt, essentially all of the advantages provided by a photoelectric control system are lost.
Another problem with current checkstand systems concerns the light intensity of the light source utilized in the system. Typically, the intensity of the light emitted by the light source, which is utilized to start and stop the conveyor belt of the checkstand, is preset significantly above the light level required to turn on the conveyor. This is required such that, as contamination builds up on the lens of the photosensor, the light source intensity can penetrate through the contamination and keep the checkstand running. Another reason the intensity of the light source is set significantly above the trip point of the photosensor is that the light intensity emitted from the light emitting diode (LED) will diminish over a period of years. As the photoelectric control system of the checkstand is expected to provide uninterrupted service for a period of 10 to 15 years or more, to insure such uninterrupted operation, the light source intensity is typically preset to a level significantly above the level of the photoelectric sensor (also referred to herein as a photosensor) required to indicate a light state. As a result, as the intensity of the light source diminishes over time, the intensity level will still be sufficient to place the photosensor in the light state. It is a necessity that uninterrupted operation of the belt on the checkstand be accomplished without any manual adjustments to the control system. Unfortunately, however, increasing the intensity of the light source compounds the foregoing problem of the checkstand system not being able to detect translucent and low profile products.
Accordingly, in view of the foregoing problems, there is a significant need for a photoelectric control system for controlling the stopping and starting of a conveyer belt for use with a checkstand which consistently detects substantially all (i.e., most) translucent and low-profile products placed on the conveyer belt so as to prevent such products from being pushed off the belt onto the scanner (typically located at the end of the belt) or off the checkstand completely, so as to eliminate the problems concerning product loss, customer throughput, productivity of checkout clerks, etc., noted above, which are associated with today's photoelectric control systems currently utilized in checkstands.